1. Field of the Invention
The invention relates to a fluidtight zip fastener, having a pair of fluidtight zip fastener carrying tapes carrying the zip fastener members and whose press-contact edge portions extending longitudinally engage on one another, each carrying tape comprising a base tape with a soft covering layer of synthetic rubber or the like, which covers at least one surface of the base tape in question, a pair of continuous coupling member rows being sewn to the zip fastener carrying tapes in a spatially offset position transversely to the longitudinal edges of the zip fastener carrying tapes in such a way that the press-contact edge portions of the soft covering layers are in contact with one another along a longitudinal plane which intersects the zip fastener at a central axis thereof and which is at right angles to the principal plane of the zip fastener, the press-contact edge portions of the zip fastener carrying tapes projecting over the longitudinal plane in question if the coupling member rows are disengaged.
2. Description of the Related Art
In a known watertight zip fastener of this type (U.S. Pat. No. 4,724,586), the coupling member rows are sewn onto the side of the particular carrying tape provided with the soft covering layer and the portions of the two carrying tapes projecting over the coupling member rows are folded round by in each case 180xc2x0 towards the side remote from said rows, accompanied by a protective covering of the sewing yarns of the coupling member rows. Even in the latter position, the press-contact edge portions of the zip fastener carrying tapes, in the vicinity of their rearwardly deflected outside, project over the coupling member rows in the case when the latter are disengaged, so that on passing into the engagement position they undergo a compression in the zip fastener principal plane and thereby bring about the sealing action. It has been found that not only the sealing, particularly when a pressure is applied to the sealing area, particularly if gastightness is desired, leaves much to be desired, but also the manufacture of such a zip fastener is complicated, time-consuming and therefore expensive due to the different successive manufacturing steps.
Mention is also made of another known watertight zip fastener having a different construction (U.S. Pat. No. 3,668,745), in which in place of continuous spiral coupling member rows which are in each case sewn to the associated carrying tape, on the outer edge portion of the base tape of the carrying tape, use is made of astride-fixed, wound metallic coupling members in such a way that despite the bending over of the base tape edge portion by 180xc2x0 in the rearward direction a firm hold is still obtained. In addition, the soft covering layers applied to the sides of the particular base tapes remote from the coupling member rows can project over the coupling member-carrying marginal portions thereof which are folded over rearwards, so that when the coupling members are in the engaged position they come into mutual pressure contact with their faces located in the zip fastener principal plane and thus ensure the sealing action. Quite apart from the fact that this is a zip fastener construction with expensive, metallic individual coupling members, it has proved disadvantageous in connection therewith that following a certain use period the sealing action does not remain adequate.
The problem of the invention is to so further develop the zip fastener of the aforementioned type that, despite a simpler construction, even during a prolonged period of use, there is a completely satisfactory sealing action both against liquids and gases, even when pressure is applied.
This problem is solved by the fluidtight zip fastener according to the invention, which is essentially characterized in that the press-contact edge portions of the zip fastener carrying tapes, if the coupling member rows are disengaged, project to such an extent over the longitudinal plane in question that said edge portions, when the coupling member rows are in engagement, are bent away from that side carrying the coupling member rows and diverge in such a way that they extend roughly at right angles to the principal plane of the zip fastener, the soft covering layers of the press-contact edge portions of the two zip fastener carrying tapes, which in each case project over the base tape, engage on one another under pressure action and thus ensure the fluidtightness condition. The concept of synthetic rubber or the like ensuring fluidtightness obviously includes all elastomers, including thermoplastics which are active in the case of pressure differences.
An increased sealing action in the closed zip fastener state can be achieved in a particularly simple manner if the portions of the soft covering layers in the vicinity of the press-contact edge portions are kept thicker than in the remaining areas of the zip fastener carrying tapes, so that the compressive forces acting against one another in the coupled state of the coupling member rows are increased. Immediately upstream of the base tape end, whose faces are enveloped by the soft covering material layer projecting over the same and are consequently protected against fraying, there is in this way an increased soft material accumulation, which in the round-terminating area ensures an overpressing, so that this counteracts the otherwise feared V-shaped expanding of the edge zones of the carrying tape edge portions.
The handling of the zip fastener, particularly during the closing process, is aided in a further advantageous embodiment of the invention in that the press-contact edge portions of the zip fastener carrying tapes which when the coupling member rows are disengaged project over the longitudinal plane in question, are so preshaped that they terminate in a plane inclined with respect to the zip fastener principal plane and form an acute angle with the latter. An angle of approximately 20 to 40xc2x0 has proved highly appropriate. The choice of the suitable angle is naturally dependent on the hardness of the material of the covering layers.
An important parameter for a satisfactory sealing function is also the dimensioning of the individual zip fastener layers. It has proved very advantageous if the soft covering layers of the two zip fastener carrying tapes have a thickness equal to or smaller than the thickness of the two base tapes. Appropriately the thickness of the base tapes is approximately 0.6 mm and the total thickness of the zip fastener carrying tapes approximately 1 mm.
The outer faces of the soft covering layers extending transversely to the zip fastener principal plane and projecting over the end of the associated base tape can be made smooth. However, it has been found that it is appropriate to provide said areas of the soft covering layers of one carrying tape, which come into contact with corresponding outer faces of the covering layers of the other carrying tape, with in each case a roughening or a profiling. It has proved advantageous if the profiling is formed by successive elevations and depressions of the outer faces extending parallel to the coupling member rows.
The invention is also directed at a special construction of the zip fastener slider, which in the conventional manner has a lower plate and an upper plate, as well as a slider wedge interconnecting the two plates. According to the invention, in the central area of the slider wedge is formed a projecting guide flange extending between the upper and lower plates and which on either side of the slider wedge separates the first two chambers receiving the coupling member rows from the two second chambers receiving the press-contact edge portions of the zip fastener carrying tapes.
The outer edge of the guide flange appropriately has a substantially constant spacing from the guide flange-carrying slider wedge.